1. Field of the Invention
The present invention relates to a process for the manufacture of pure metal chlorides, and more particularly relates to a process for manufacturing pure aluminum chloride (AlCl.sub.3), silicon tetrachloride (SiCl.sub.4), and titanium tetrachloride (TiCl.sub.4).
2. General Background
The production of pure metal chlorides, particularly aluminum chloride, is of particular significance in the manufacture of aluminum metal. Two methods are presently used to manufacture aluminum. The first is the 100 year old Hall process and the second is the relatively new Alcoa process.
The Hall process requires a feed of pure alumina which heretofore has been produced commercially solely by the Bayer process which requires a supply of high grade bauxite.
The Alcoa process is used to produce aluminum metal by electrolyzing aluminum chloride produced by carbochlorinating Bayer alumina.
It can be seen that both of the above processes require a supply of high grade bauxite in order to obtain the necessary intermediates of alumina and/or aluminum chloride. This creates a problem as the supply of high grade bauxites is limited and occurs only in a limited number of countries. This problem creates a need for a method of producing pure aluminum chloride chloride with the use of an ore other than bauxite. Patents aimed at the production of aluminum chloride of which applicant is aware include the following:
U.S. Pat. No. 3,935,297, entitled "Carbo-Chlorination Of Aluminum Phosphate" (AlPO.sub.4) discloses the process wherein aluminum phosphate ore is chlorinated to yield aluminum chloride, phosphorous chlorides and phosphorous oxy chloride.
U.S. Pat. Nos. 3,937,786 and 3,950,485 disclose processes for the production of aluminum chloride from raw materials such as coal, slate or bituminous shale. The raw material is chlorinated and is required to have an ash content of at least 30% by weight with an aluminum content of the ash being at least 20% calculated as Al.sub.2 O.sub.3.
U.S. Pat. No. 3,956,454 discloses a process for using low grade carbonaceous material to form aluminum tri-chloride. A low grade aluminous material is ground with a suitable reductant and mixed together and formed into tablets or brickets for chlorinating a compresses or paste-like form.
U.S. Pat. No. 4,083,923, discloses a process for the production of aluminum chloride by the carbo chlorination of such ores as clay, bauxites and laterytes wherein the aluminum chloride produced is purified by passing the aluminum chloride through a suitable metalic solvent after the aluminum chloride has been separated from the FeCl.sub.3 also produced. The AlCl.sub.3 and the FeCl.sub.3 are contained in a molten salt solvent from which they are recovered and then separated.
U.S. Pat. No. 4,083,927, of which applicant is the inventor, discloses a process for the carbo-chlorination of koalinitic ores wherein catalytic amounts of boron chloride are added to the carbo-chlorination step.
U.S. Pat. No. 4,220,629, of which applicant is a co-inventor, discloses a process for the manufacture of metal chlorides by the double decomposition reaction between a metal chlorinating agent and a metal oxide in the presence of small amounts of boron chloride.
Although the above patents disclose methods for the production of aluminum chloride, the ores from which production is possible is limited. The present invention solves this problem by providing a process which may be utilized with a wide variety of aluminous ores. The present invention also results in the production of pure TiCl.sub.4 which is valuable as titanium is a rare and valuable metal used in various industries.